OverviewAchilles tendinitis is present when your Achilles tendon becomes inflamed or irritated.Often, Achilles tendinitis results from sports that place a lot of stress on your calf muscles and Achilles tendon, such as basketball. Achilles tendinitis also is often associated with a sudden increase in the intensity or frequency of exercise.When treated promptly, Achilles tendinitis is often short-lived. Left untreated, Achilles tendinitis could cause persistent pain or cause your tendon to tear (rupture). If so, you may need surgery to correct the damage.